ref(preprod): Add organization_slug to size analysis log (#112194)

Add `organization_slug` to the size analysis metrics log entry in
preprod tasks for easier debugging and log correlation when
investigating size analysis issues.

---------

Co-authored-by: Claude Opus 4.6 <noreply@example.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: 3 people

src/sentry/preprod/tasks.py

@@ -562,6 +562,7 @@ def _assemble_preprod_artifact_size_analysis(
                 "was_created": was_created,
                 "project_id": project.id,
                 "organization_id": org_id,
+                "organization_slug": organization.slug,
             },
         )